LPW TECHNOLOGY
CASE STUDY 07:
PLASMA SPHEROIDISATION
07
Plasma Spheroidisation for
improved metal powder flow
and packing properties
To achieve optimum flow
characteristics and high packing
density, an ideal Additive
Manufacturing metal powder should
be highly spherical in shape with no
satellites. As spherical particles have
minimum surface area to volume
ratio this brings an added advantage
in principle, of reduced surface
contamination e.g. oxygen pick up.
Increased particle sphericity can
improve powder feeding, resulting in
smoother layers, improved packing
density, increased heat conduction
in the powder bed and an enhanced
melting profile.
selected according to the required
performance of the final part,
reproducible behaviour of the powder
throughout the process is key to a
successful build.
Generating a component by Additive
Manufacturing (AM), also known as
metal 3D Printing, relies on building
the final design through a series of
many thousands of layers. Whilst
different metal powders can be
This case study presents the results of
LPW’s plasma spheroidisation process
on morphology, flow, and packing
properties of three different metallic
powders - pure Tungsten (W), Ti6Al4V,
and pure Tantalum (Ta).
LPW TECHNOLOGY LTD
16 Berkeley Court, Manor Park
Runcorn, Cheshire WA7 1TQ
United Kingdom
CONTACT
T: +44 (0) 1928 240 530
E: [email protected]
Plasma spheroidisation
In principle, any metallic powder
can be plasma treated to improve
the flow and packing properties of
low sphericity, irregular, sponge-like,
agglomerated and angular metallic
powders produced by other methods
e.g. water atomisation, chemical and
mechanical processes, and standard
gas-atomisation.
Results
Several trials have been performed for
each powder feedstock to determine
the optimum processing parameters.
The powder samples were fully
characterised after each plasma
treatment trial and compared with
those of the starting feedstock.
The results demonstrate that when
spheroidisation parameters are
optimised for the particular feedstock,
particle morphology, powder flow and
packing properties are significantly
improved.
LPW TECHNOLOGY LTD
LPW TECHNOLOGY
CASE STUDY 07:
PLASMA SPHEROIDISATION
Before Plasma Treatment
After Plasma Treatment
Product
Ti-64 feedstock (HDH and mechanically crushed)
Ti-64 spherical
Particle Size, µm
45-105 µm
45-105 µm
Hall Flow rate, sec/50g
47.31
22.3
App. Density, g/cc
N/A
2.6
Tap Density, g/cc
2.2
3.0
Shape analysis
Circularity: D10: 0.556, D50: 0.774, D90: 0.937
Elongation: D10: 0.083, D50: 0.260, D90: 0.428
Circularity: D10: 0.81, D50: 0.989, D90: 0.995
Elongation: D10: 0.008, D50: 0.044, D90: 0.366
Morphology SEM - x1000 mag
Figure 1 - Comparison of Ti64 before spheroidisation (L)
and post-spheroidisation (R)
Figure 1 shows one of the most
commonly used Ti-based alloys:
Ti6Al4V Grade 23. The starting
powder, produced by mechanically
crushing “embrittled” ingots via a
Hydride-De-Hydride (HDH) process,
is angular and elongated. Considering
the particle size the flow rate is low
and the tap density is less than 50%
LPW TECHNOLOGY LTD
16 Berkeley Court, Manor Park
Runcorn, Cheshire WA7 1TQ
United Kingdom
CONTACT
T: +44 (0) 1928 240 530
E: [email protected]
of the theoretical bulk density for this
material. The SEM image shows that
post spheroidisation, the particles are
almost perfectly spherical i.e. with a
circularity close to 1, [Circularity: D10:
0.81, D50: 0.989, D90: 0.995], flow
time is improved by a factor of two
and tap density is increased to almost
60% of the theoretical bulk density.
LPW TECHNOLOGY LTD
LPW TECHNOLOGY
CASE STUDY 07:
PLASMA SPHEROIDISATION
Before Plasma Treatment
After Plasma Treatment
Product
W feedstock
W spherical
Particle Size, µm
15-45 µm
15-45 µm
Hall Flow rate, sec/50g
7.5
5
Tap Density, g/cc
11.2
14.3
Shape analysis
Circularity: D10: 0.70, D50: 0.89, D90: 0.95
Elongation: D10: 0.05, D50: 0.17, D90: 0.36
Circularity: D10: 0.80, D50: 0.95, D90: 0.98
Elongation: D10: 0.02, D50: 0.15, D90: 0.33
Morphology SEM - x1000 mag
Figure 2 Comparison of Tungsten before spheroidisation (L)
and post-spheroidisation (R)
Figure 2 shows the results for the
refractory metal Tungsten, which at
3422 °C has the highest melting point
of all metals in its pure form. The
tungsten feedstock was produced
by reducing Tungsten oxides and
demonstrates angularity, although
both flow and packing density (~58%
LPW TECHNOLOGY LTD
16 Berkeley Court, Manor Park
Runcorn, Cheshire WA7 1TQ
United Kingdom
CONTACT
T: +44 (0) 1928 240 530
E: [email protected]
of the theoretical bulk density)
are relatively good. After plasma
treatment, the majority of the powder
particles are shown to be spherical
and both flow and packing (~74%
of the theoretical bulk density) are
improved.
LPW TECHNOLOGY LTD
LPW TECHNOLOGY
CASE STUDY 07:
PLASMA SPHEROIDISATION
Before Plasma Treatment
After Plasma Treatment
Product
Ta feedstock (dendritic)
Ta Spherical
Particle Size, µm
15-45 µm
15-45 µm
Hall Flow rate, sec/50g
17.4
5.2
App. Density, g/cc
N/A
N/A
Tap Density, g/cc
8.32
11.16
Shape analysis
N/A
Circularity: D10: 0.790, D50: 0.989, D90: 0.996
Elongation: D10: 0.007, D50: 0.050, D90: 0.276
Morphology SEM – x275 mag
Figure 3 Comparison of Tantalum before spheroidisation (L)
and post-spheroidisation (R)
Figure 3 shows the results for
refractory metal tantalum, melting
point 3017 °C. The tantalum powder
was produced by electrolysis of
a solid feedstock and has a very
irregular, dendritic shape. The flow
is slow for the density of material
and tap density is less than 50% of
the theoretical bulk density. After
optimised spheroidisation the powder
particles become highly spherical
and both the flow and packing (~67%
of the theoretical bulk density) are
significantly improved.
Plasma Spheroidisation
Conclusion
LPW TECHNOLOGY LTD
16 Berkeley Court, Manor Park
Runcorn, Cheshire WA7 1TQ
United Kingdom
CONTACT
T: +44 (0) 1928 240 530
E: [email protected]
Morphology and packing density
have a significant effect on the quality
of the powder layer and melting
behaviour, depending on deposition
system. Plasma Spheroidisation at LPW
has been shown to be an effective
method of controlling the shape,
flow and packing characteristics to
defined specifications across a range
of metallic powders to deliver reliable,
reproducible performance.
At LPW, we have a wealth of expertise
in metal Additive Manufacturing AM,
metal 3D Printing, and extensive
experience of working with leading
companies within the aerospace,
biomedical, and automotive industries.
We utilise this knowledge and the
capabilities of plasma technology to
provide solutions across a wide range
of industries and AM platforms.
LPW TECHNOLOGY LTD